Compound Interest Calculator
See how compounding grows a one-time amount — and how the frequency changes the outcome.
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Frequently asked questions
What is compound interest?
Compound interest is interest earned on both the original principal and on the interest already accumulated. Because interest earns interest, your money grows faster over time — often called the eighth wonder of the world.
What is the compound interest formula?
A = P × (1 + r/n)^(n×t), where P is the principal, r is the annual rate (as a decimal), n is how many times interest compounds per year, and t is the time in years. Interest = A − P.
Does compounding frequency matter?
Yes. The more often interest compounds — yearly, half-yearly, quarterly, monthly — the more you earn, because interest starts earning interest sooner. The difference grows over long periods.
How is it different from simple interest?
Simple interest is calculated only on the principal and grows in a straight line. Compound interest is calculated on principal plus accumulated interest, so it accelerates over time.